1. Field of the Invention
The invention relates to a ground anchor or rock anchor having an anchor tension member composed of one or more individual elements and having a corrosion-protected anchor head design.
2. Description of the Background Art
Ground and rock anchors are typically used when it is necessary to transmit forces in the region of the anchor head to deeper soil strata. For this purpose, generic anchors have an anchor tension member, which can be composed, for example, of a single bar anchor, which as a general rule has a continuous external thread. Such anchors are known in the form of rock bolts or soil nails, which are either bonded to the wall of the drilled hole over their entire length by the introduction of an injected grout and are subsequently tensioned, or in the type known as post-tensioned anchors are anchored only in the area of the base of the drilled hole and are prestressed at the exposed end. The tensioning or prestressing is accomplished by an anchor nut that is screwed onto the thread of the bar anchor and bears against an anchor plate.
In addition, conventional anchors with an anchor tension member composed of multiple individual elements are known. The individual elements are usually composed of steel wire strands that are anchored to the wall of the drilled hole in the innermost part of the drilled hole. As a rule, such anchors are produced in the form of post-tensioned anchors. Since the wire strands have no external threads, the anchor provides a head block in the vicinity of the anchor head, in which the steel wire strands are frictionally held by anchoring wedges.
Ground and rock anchors are used for both temporary and permanent applications, with permanent use requiring a design that is suitable for protecting against corrosion. In this context, a distinction is drawn between corrosion protection in the region inside the drilled hole, in which passivation is achieved by injecting grout into the drilled hole, and which sometimes is supplemented by plastic sheathing, [and protection outside the hole]. In the region of the anchor head, which is to say outside the drilled hole, corrosion protection is achieved by covering the exposed parts with a corrosion protection compound, such as grease, for example.
From DE 203 14 997 U1 is known a prestressed ground anchor with a plurality of steel wire strands as the anchor tension member, which is introduced into a drilled hole and is anchored at the exposed end in an anchor plate by a head block and wedges. The free ends of the individual steel wire strands project past the head block so that their ends can be gripped by a tensioning jack in the event of the retensioning or removal of individual strands.
In order to ensure corrosion protection in the area of the anchor head, a cap that encloses the head block and the projecting ends of the steel wire strands is provided; the cap is filled with a corrosion protection compound and is fastened to the anchor plate at a circumferential flange using screws.
This type of corrosion protection has been proven in practice. However, it has been noted that the anchor head is also frequently provided with protective paint at a later time, which covers the heads of the fastening screws as well. Especially in the event of a later removal of the cap as part of maintenance or repair work, it is then necessary to remove paint residue from the screw heads, which entails considerable effort.